I am not aware of any reliable research-based recipes for canning salsa substituting citric acid for lemon, lime juice or vinegar.  There are safe substitutions you can make, and they are found on page 3-4 of our canning salsa publication.
https://extension.oregonstate.edu/catalog/pub/pnw-395-salsa-recipes-canning
It would be safe to freeze your salsa and substitute citric acid.  
Salsa is one of those interesting foods we can that we need to be very careful to do it safely.  We are mixing high and low acid foods together and then processing for a short time so that we keep the texture like salsa.  If not done correctly it could be very risky because most salsas are consumed right out of the jar and not used in cooked products or boiled for 10 minutes before eating as an added margin of safety to detoxify botulism toxin if it happens to be there.  
I personally would not risk it.  

Here are some guidelines for preserving safe and healthy salsas. 

1. Obtain current, tested recipes and instructions and follow them.
2. Use high-quality, just-ripe tomatoes, peppers, onions and garlic. Do not use tomatoes that are overripe or from frost-killed vines.
3. Use the amount of tomatoes the recipe calls for. You can use or combine red, green or heirloom tomatoes or tomatillos as long as the amount remains the same.
4. Use the amount of peppers the recipe calls for. Mix and match peppers to vary heat, appearance and flavor. Handle peppers with gloves.
5. Use the amount and type of acid the recipe calls for. Vinegar or bottled lemon/lime juice ensures the safety of the product. Breaking this law could be life threatening.
6. Dried spices may be added or deleted as desired. These may include salt, ground pepper, dried chili pepper, coriander, cumin and oregano.
7. Don’t add more vegetables or fresh herbs than the recipe calls for.
8. Don’t add thickeners.
9. Use the processing method for the length of time specified in the recipe. Salsa can be safely stored in the refrigerator for several weeks or frozen for months without processing.
10. It’s not safe to can your own original salsa recipe. Refrigerate or freeze it instead.

Thanks for using Ask Extension.
Nellie Oehler